1. Field of the Invention
The present invention relates to a method for erasing data from a CD-RW (CD rewriteable) disc, and a CD-RW recording apparatus that performs this erasing method, so that information for each CD-RW disc that is stored in the CD-RW recording apparatus or in a host computer connected thereto can be reused even after the CD-RW disc has been blanked.
2. Related Arts
Two methods are available for erasing CD-RW discs by physical erasing or logical erasing. For physical erasing, the method used involves the tracing of a track using a laser beam that is set at an erasing level and the deletion of bits by restoring the surface of a disk to the original unrecorded state. For logical erasing, a method is used whereby recorded data is overwritten by logic 0 data. Further, two modes are available for the erasure of CD-RW discs: the erasure of an entire disc and the erasure of a last track. To erase an entire disc using the logical erasing method, the entire PMA (Program Memory Area) is logically erased. Otherwise, the entire PMA area and all the read-in area may be erased when a finalizing process has been performed. TOC (Table of Contents) data such as the numbers of tracks (corresponding to music pieces for an audio disc) recorded in the program area of a CD-RW disc, and position information are recorded in the PMA area and the read-in area. When these areas on a CD-RW have been logically erased, a CD-RW recording apparatus determines that no tracks have been recorded on the CD-RW disc, and a new track can be written, beginning at the start position in the program area.
To erase the last track, normally, track information corresponding to the last track is logically erased from the PMA area of a CD-RW that has not been finalized (namely, the read-in area is not in use). In this manner, when the track information corresponding to the last track of a CD-RW disc has been erased, a CD-RW recording apparatus will determine that the CD-RW disc has no last track, and that a new track can be written beginning at the start position for the last track in the program area. Incidentally, by repeatedly performing such a last track erasure, all tracks on a CD-RW disc can be progressively erased beginning from the end track and proceeding backward to the top track.
In addition to information concerning each track, during the recording process, unique disc identification information (a disc ID), which is readable by a CD-RW recording apparatus, is entered in the PMA area of a CD-RW disc. Thus, when a CD-RW disc on which no disk ID has been recorded is loaded into a CD-RW recording apparatus, the apparatus may detect that the disc bears no disc ID. The CD-RW recording apparatus determines that the CD-RW disc has not been registered, and using an arbitrary code, the recording apparatus generates a disc ID and writes the disc ID in the PMA area of the CD-RW disc. Since disc IDs are employed, the information concerning each CD-RW disc can be managed by the CD-RW recording apparatus, or by a host computer that is connected to the recording apparatus. Then, to write data into a CD-RW disc, for example, OPC (Optimum Power Control) is exercised. According to this operation, prior to the actual writing of data to the program area, a preliminary writing process is performed for a PCA (Power Calibration Area) area, the innermost area on a disc, by sequentially changing the recording laser power at different speeds (uni-speed, double speed, etc.) that can be used for the actual recording. Then, the written data are read out to determine the optimum recording laser power that provides the best replay signal characteristic. The initial value of the recording laser power is then set to the obtained value, and the actual recording is begun. The initial value determined for the recording laser power can be repetitively used so long as the same CD-RW recording apparatus performs the data recording for the same CD-RW disc at the same recording speed.
The optimal results (parameters such as the recording speed and the initial recording laser power value, hereinafter referred to as OPC parameters) obtained by the OPC are stored together with the disc ID of the CD-RW disc in the memory (an EEPROM, a flash memory, a hard disk, etc.) of the CD-RW recording apparatus or the host computer. Then, when the CD-RW disc is again loaded into the CD-RW recording apparatus and the disc ID is read from the PMA area, if the disc ID is registered in the memory, the corresponding OPC parameters will be available such that the recording speed and the initial recording laser power value can be automatically set to perform the actual recording. Since this function (called an OPC value memorization function) is employed, the OPC execution time (7 to 15 seconds each time), which is required each time a CD-RW disc is loaded into a CD-RW recording apparatus, can be saved whereby the waiting time before the initiation of the actual recording can be reduced.
However, according to the conventional erasing method, a disc ID is erased at the same time as the PMA area is erased, hence the OPC parameters for a subject CD-RW disc cannot be read and employed, even though the OPC parameters may be stored in the memory of the CD-RW recording apparatus or the host computer, and the OPC must be repeated.